Early-flowering plants were selected from a field population of Lupinus angustifolius and from field and X-ray-treated populations of L. digitatus. One naturally-occurring dominant gene for earliness was isolated in each species, together with an artificially-induced recessive, unlinked to the dominant, in L. digitatus. To evaluate the different genotypes for breeding purposes, and to analyse the factors of the Western Australian environment controlling their flowering time, sowings of all genotypes were made with and without artificial vernalization, over a range of sowing dates, and in a range of environments differing mainly in temperature. Effects on flower initiation were estimated from times of flowering and first flowering node numbers. Flowering of L. angustifolius was found to be controlled mainly by its vernalization requirement. In L. digitatus, vernalization, a dark period inhibition, and an acceleration of flower initiation by high temperatures all appeared to be important. The dominant genes of both species removed all effective vernalization requirement, while the recessive in L. digitatus may have removed or relaxed a dark period inhibition. It was concluded that all three earliness genes would be useful in extending the cultivation ranges of the two species.

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